/*
 * Copyright 2012 Marsrutai.lt
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package lt.marsrutai.mobile.android.service.impl;

import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.IBinder;
import android.os.Looper;
import android.os.Message;

/**
 * This is a enhanced copy of android.app.IntentService class.
 *
 * Intent requests can be canceled by sending a special intent.
 *
 * @author Martynas
 */
public abstract class CancelableIntentService extends Service {

    private volatile Looper mServiceLooper;
    private volatile ServiceHandler mServiceHandler;
    private String mName;
    private boolean mRedelivery;

    private final class ServiceHandler extends Handler {

        public ServiceHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            if (null != msg.obj) {
                onHandleIntent((Intent) msg.obj);
            }

            stopSelf(msg.arg1);
        }
    }

    /**
     * Creates an IntentService. Invoked by your subclass's constructor.
     *
     * @param name
     *            Used to name the worker thread, important only for debugging.
     */
    public CancelableIntentService(String name) {
        super();
        mName = name;
    }

    /**
     * Sets intent redelivery preferences. Usually called from the constructor with your preferred semantics.
     *
     * <p>
     * If enabled is true, {@link #onStartCommand(Intent, int, int)} will return {@link Service#START_REDELIVER_INTENT},
     * so if this process dies before {@link #onHandleIntent(Intent)} returns, the process will be restarted and the
     * intent redelivered. If multiple Intents have been sent, only the most recent one is guaranteed to be redelivered.
     *
     * <p>
     * If enabled is false (the default), {@link #onStartCommand(Intent, int, int)} will return
     * {@link Service#START_NOT_STICKY}, and if the process dies, the Intent dies along with it.
     */
    public void setIntentRedelivery(boolean enabled) {
        mRedelivery = enabled;
    }

    @Override
    public void onCreate() {
        // TODO: It would be nice to have an option to hold a partial wakelock
        // during processing, and to have a static startService(Context, Intent)
        // method that would launch the service & hand off a wakelock.

        super.onCreate();
        HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
        thread.start();

        mServiceLooper = thread.getLooper();
        mServiceHandler = new ServiceHandler(mServiceLooper);
    }

    /**
     * Puts both, work requests and cancel work requests to the same handler queue, because Service.stopSelf(int) must be
     * called for every startId.
     */
    @Override
    public void onStart(Intent intent, int startId) {

        String key = getRequestKey(intent);
        Boolean isCancelIntent = isCancelIntent(intent);

        if (isCancelIntent) {
            mServiceHandler.removeMessages(key.hashCode());
        }

        Message msg = mServiceHandler.obtainMessage();
        msg.arg1 = startId;
        msg.obj = isCancelIntent ? null : intent;
        msg.what = key.hashCode();
        mServiceHandler.sendMessage(msg);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        onStart(intent, startId);
        return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        mServiceLooper.quit();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    /**
     * This method is invoked on the worker thread with a request to process. Only one Intent is processed at a time,
     * but the processing happens on a worker thread that runs independently from other application logic. So, if this
     * code takes a long time, it will hold up other requests to the same IntentService, but it will not hold up
     * anything else.
     *
     * @param intent
     *            The value passed to {@link android.content.Context#startService(Intent)}.
     */
    protected abstract void onHandleIntent(Intent intent);

    /**
     * Returns whether this intent represents cancel action.
     *
     * @param intent
     * @return
     */
    protected abstract boolean isCancelIntent(Intent intent);

    /**
     * Gets key from the intent. Keys are used to track tasks.
     *
     * @param intent
     * @return
     */
    protected abstract String getRequestKey(Intent intent);
}
